摘要
基于中国地震科学探测台阵在鄂尔多斯及周边地区布设的461个地震台为期2年的地震观测资料,采用背景噪声层析成像方法,研究获得了鄂尔多斯及周边地区5-46 s周期、分辨率高达0.3°×0.3°的瑞雷面波相速度分布图像。与基于程函方程的地震面波成像结果对比看出,噪声层析成像在较短周期具有明显的优势(5-16 s),可以获得更高分辨率的成像结果。短周期(5-10 s)的相速度分布揭示,河套盆地、太原盆地和运城盆地等均表现为显著的低速异常,表明这些盆地的新生代沉积较厚,临汾盆地为弱低速异常,推测其沉积层相对较薄;鄂尔多斯地块内部浅层速度较低,与该地区中生代具有较厚的沉积相一致;大同火山区为高速异常,可能是由该地区分布的新生代玄武岩引起的。鄂尔多斯内部中上地壳存在明显的北东向高速异常带,推测很可能与鄂尔多斯地块的基底拼合有关。中长周期(20-44 s)的相速度成像结果显示,鄂尔多斯地块表现为明显的高速异常,该异常在灵石隆起和临汾盆地一带可向东延伸至太行山造山带,推测这一地区在华北克拉通破坏过程中属于破坏较轻的地区,保留了部分高速的岩石圈根。大同火山区及河套盆地地区具有明显的低速异常,随着周期的增加低速异常逐渐集中分布在大同火山区附近,推测河套盆地深部热作用可能源自其东部大同火山区附近的深部地幔。
Based on the 2-year seismic observation data of 461 seismic stations deployed in the Ordos and surrounding areas by the ChinArray,we use the ambient noise tomography method to obtain the Rayleigh surface wave phase velocity(5-46 s)images whose resolution is up to 0.3×0.3 degree.Compared with the seismic surface wave imaging results based on the Eikonal equation,we find that ambient noise tomography has a clear advantage in shorter periods(5-16 s)and higher resolution imaging.The short-period(5-10 s)phase velocity distribution reveals that the Hetao basin,Taiyuan basin and Yuncheng basin all exhibit significant lowvelocity anomalies,indicating that these basins have thicker Cenozoic deposits.And in the Linfen basin,there is a weak low-velocity anomaly and a relatively thin sediment layer.Also,the Ordos block has a low-velocity anomaly,consistent with the Mesozoic thick deposit in this area;the Datong volcanic area shows a high-velocity anomaly,which may be caused by the distribution of Cenozoic basalt in this area.The mid-long period(20-44 s)phase velocity imaging results show that the Ordos block exhibits an obvious high-velocity anomaly.The anomaly can extend eastward to the Taihang mountain through the Lingshi uplift and Linfen basin.We suspect that the area is with less damage in the evolution process of the North China Craton and retains part high-velocity lithosphere roots.The Datong volcanic area and Hetao basin area have low-velocity anomalies.As the period increases,the low-velocity anomalies are gradually concentrated near the Datong volcanic area.We speculate that the deep thermal effect in the Hetao basin may originate from the deep mantle near the Datong volcanic area in the east.
作者
刘靖
吴建平
王未来
蔡光耀
王薇
Liu Jing;Wu Jianping;Wang Weilai;Cai Guangyao;Wang Wei(Institute of Geophysics,China Earthquake Administration,Beijing 100081,China;Key Laboratory of Seismic Observation and Geophysical Imaging,Institute of Geophysics,China Earthquake Administration,Beijing 100081,China)
出处
《地震学报》
CSCD
北大核心
2021年第2期152-167,I0001,共17页
Acta Seismologica Sinica
基金
国家自然科学基金(41774102,41974058,41804057,41704064,41774067)
国家重点研发计划(2017YFC0404901)
中国地震局地球物理研究所基本科研业务费专项(DQJB20K41,DQJB16A03,DQJB17A01)共同资助。
